1. Field of the Invention
The present invention relates to detection of gamma-rays, and more specifically, it relates to scintillator based gamma-ray spectrometers.
2. Description of Related Art
Currently, small scintillator-based hand-held or back pack instruments dominate the available gamma-ray detection and identification tools available to the wide community tasked with measuring these emissions. Many parameters, e.g., weight, ease of use, ruggedness, battery life-time, gamma-ray sensitivity, and specificity are addressed by the many vendors of these instruments. Ultimately, cost is traded against performance by the purchasing entity. This generally precludes the semiconductor (germanium) based instruments from almost all applications due to the marked difference in cost (5×+). Most of the commercially available instruments are based on NaI scintillators as they are readily available, moderately efficient, moderately rugged, and can deliver modest spectral resolution at a tolerable cost. The spectral resolution of the NaI based instrument enables some isotope identification. A new small Compton suppressed scintillator instrument having a cost similar to the current instruments but having a much improved response is desired.
The utility of existing forward-deployed hand-held radiation detectors is debatable. Abundant anecdotal evidence suggests their utility is very limited. The reason is clear: low-Z detectors have an extremely low probability for full gamma-ray energy deposition. This intrinsic limitation is compounded by the need to make the fielded detectors as small as possible. A poorly performing radiation detector hampered by false alarms is perhaps worse than no detector at all—it may cause the user to dismiss more practical alternatives. One obvious alternative, replacing the scintillator with a high-resolution germanium crystal, is problematic in at least two areas: germanium is comparatively expensive and the crystal would nonetheless itself need Compton suppression due to size, low atomic number, etc. Rather than make incremental improvements, the present invention makes three improvements that collectively transform these devices into serious perimeter defense stalwarts.